Within the last two decades, cellular phones have become incorporated into almost every aspect of daily life. Cellular phones are truly ubiquitous devices which have achieved their usefulness and relatively low cost from continuing advances in modern microelectronics. As microelectronic memory densities and processing power have increased year after year, cellular phones have benefited from the commensurate availability of increasing computing power. Coupled with advances in radio frequency (RF) integrated circuits, power management microelectronics, and battery charge density improvements, the size of a typical cellular phone has been reduced to a package which fits easily in the palm of a hand.
The computational power now available in modern 3G (third generation) cellular phones rivals that of wireless personal digital assistants, so much so that there is presently almost no distinction between cellular phones, wireless communication devices targeted for email (e.g., BlackBerry™), and wireless personal digital assistants (wPDAs) (e.g. Treo™, PalmPilot™, etc.). Any device which provides bidirectional audio communication over a cellular radio network and possesses sufficient local processing capability to control the device and execute stored user applications (e.g., text messaging, email, calculator, web browser, games) is often referred to as a “smart phone.” The term “personal mobile communication devices” (PMCDs) more broadly comprises a class of devices which includes, but is not limited to, “smart phones,” wireless PDAs, and cellular phones, as well as other devices for communicating or processing speech which possess various degrees and combinations of embedded processing power and network connectivity (e.g., Apple™ iPhone™).
One problem suffered by conventional PMCDs is that they have inherited many features of their present user interface designs directly from the traditional computer and cellular phone industries. Today's PMCD user interface may include a graphical user interface (GUI) displayed to the user on an embedded liquid crystal display (LCD) or thin-film transistor (TFT) graphical display device, a cursor control feature, possibly one or more function buttons, and a keypad or full keyboard, as well as a microphone and a speaker. The continually shrinking package size of these devices, however, leads to several user interface problems. For instance, in order to accommodate a full keyboard, each of the keys are made extremely small so that the entire keyboard may be fitted onto the device even when a fold-out or slide-out keyboard design is used. The reduced key size can present frustrating challenges to users whose fingers may be too large to type comfortably. Further, within a typical GUI-based environment, some user actions can only be carried out by traversing multiple levels of menus of the graphical user interface. Often the cursor controller present on the device is insufficient or clumsy for navigating a GUI. Many PMCDs suffer from these problems.
Thus, there exists a need and opportunity for improvements in human-machine interface techniques and technologies which can offer much more natural interactions between the user and the PMCD in which the user is not constrained to interact with a PMCD solely through manipulation of buttons, keys, cursors, or other GUIs.
To improve and add additional functionality to the user interface, a PMCD may include one or more types of transducers. One example of a transducer included in several higher-end PMCDs is the accelerometer. The usefulness of an accelerometer arises from its ability to sense minute accelerations of the PMCD resulting from changes in kinetic forces as well as gravitational forces acting upon the device. For instance, an accelerometer may be used to detect user gestures such as strikes of the PMCD against an external body, or, conversely, the strike of an external body against the PMCD. Such a gestural event, if caused by the user, may be described as a “tap” or a “hit” of the device. This “tap” signal can be captured, recognized, and mapped to a specific user interface function to perform a useful action. An accelerometer may also be used to detect if the device has been dropped or if the device's orientation with respect to gravity has changed (e.g., if the device has been tilted) or even to detect if the device has been picked up in preparation for answering a call.
A large drawback to including accelerometers in PMCDs, however, is cost. Accelerometers are not typically included in PMCDs targeted at lower-cost device markets, thus their functionality, correspondingly, is not available on many devices. Further, many PMCD already in use do not contain accelerometers, so there is no means by which to provide these devices with such functionality.
Another example of a transducer which is included in PMCDs is the microphone. Although not responsive to acceleration of the PMCD like the accelerometer, the microphone is responsive to speech, music, and other sound waves and operates to convert speech and other sounds into electrical signals. Compared with an accelerometer, a microphone is a relatively inexpensive device which can be used as an inexpensive substitute to provide a gesture sensing capability similar to that of the accelerometer.